Hardened steel gouges

[John K Jordan]

I don't disagree with the comments that hardening and annealing steel is involved and may need to be very exacting to get consistently excellent results. Most people probably should not try it. Leave it to the professionals.
...
When I wear my tools down to a point where they are too short to use and where they aren't hardened, I am unlikely to just try to re-harden them. ...

That's interesting, Brice. I'm hoping soon to cut and machine some strips of O1 steel to make some tools and harden. A friend has a small electric kiln I could borrow but I plan to first try the two-brick kiln method, oil quenching and a toaster oven to temper, recommended by some instructions I've read. For starters I want to make some 1/8" thick scrapers and a tool to let me cut morse tapers more easily.

Have you ever tried to harden HSS steel with your equipment? Reading the experienced descriptions on a knifemaking forum scared me away. I was told one issue with rehardening a HSS gouge might be the need to know the specific composition of a given tool since different HSSs can require different processes. Is that right?

JKJ

[Brice Rogers]

John, I think that the temperatures that I use for high carbon steel are the same or similar to HSS. In fact, I have rehardened a couple of drill bits (long story) as well as some drill bits that I turned into small scrapers for hollow forms.

I heat to perhaps 50 degrees above the Curie Temperature when hardening. The Curie temperature is the point where the steel is no longer magnetic and for steel is, IIRC, somewhere around 1400 F. I read that it is advised that I do a soak at that temperature, but the parts that I do are pretty small and I haven't had bad results.

There is some info on-line by various knife makers and also steel sellers. Here is one that describes some temperatures for O1.
https://www.hudsontoolsteel.com/technical-data/steelO1

I see that the ultimate hardness for the 01 steel from that seller varies from 62 to 65 Rockwell. So, because I am doing this by the seat of my pants, I might end up with 65 RC or 62 RC or maybe even a little less. But I'm not making a mission critical part - - just a cutter and I probably won't notice the difference.

There is an interesting show on Cable/satellite called "Forged in Fire". You'll see people hardening knives and swords with only a gas forge and oil quench tank.

BTW, one of my biggest problems is scale during heat treat. The pro's use use some gas to remove oxygen from the heat treat box or use a neutral to slightly carbonizing flame in their forges. I have an experiment planned to precoat my next cutter with boric acid as an anti-scale treatment. There are some commercial anti-scale chemicals but I haven't investigated. I tried borax washing soda and while it worked well for anti-scale, it was so hard that it was very difficult to remove - - even with a file.

[John K Jordan]

John, I think that the temperatures that I use for high carbon steel are the same or similar to HSS. ...

I see that the ultimate hardness for the 01 steel from that seller varies from 62 to 65 Rockwell. So, because I am doing this by the seat of my pants, I might end up with 65 RC or 62 RC or maybe even a little less. But I'm not making a mission critical part - - just a cutter and I probably won't notice the difference.
...

I'm lead to believe working with O1 tool steel is relatively easy and the temperatures are much lower than needed for HSS. This is one reference I've found for M2 HSS.

Critical Temperature:
Ac1: 1530°F (832°C) Ac3: 1610°F (877°C)
Ar1: 1430°F (777°C) Ar3: 1380°F (749°C)

Preheating: To minimize distortion and stresses in large or complex tools use a double preheat. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1100°F (593°C) equalize, then heat to 1450-1550°F (788-843°C). For normal tools, use only the second temperature range as a single preheating treatment.
Austenitizing (High Heat): Heat rapidly from the preheat.
For Cutting Tools:
Furnace: 2200-2250°F (1204-1232°C)
Salt: 2175-2225°F (1191-1218°C)
To maximize toughness, use the lowest temperature.
To maximize hot hardness, use the highest temperature.
For punches, dies, and tools that require maximum
toughness without hot hardness:
Furnace: 2075-2175°F (1175-1191°C)
Salt: 2050-2150°F (1121-1177°C)

The 2000F temps are a bit intimidating as are the 1000F+ for tempering (compared to the 400F for O1.)

Recommended for the 10V (that Thompson uses) is apparently 2050F for 45 minutes for hardening with triple tempering at 1025F.

JKJ

[Brice Rogers]

Interesting. Thanks for sharing.

Yes the 2100 plus range is very hot and beyond my kiln.

[Thom Sturgill]

Alan Lacer has a good video on making tools with O1 steel. I have made a few hook tools using his methods which are heating with mapp gas and quenching in Olive Oil, then baking in the oven to temper. Since O1 can be easily re-hardened it does not matter if only the cutting edge is hard. A1 is air quenched, which is even easier. Of course as turning tools they do not keep an edge long.

[Brice Rogers]

Thom, thanks for your comments. I'm going to look at that tomorrow.

I've been meaning to ask this question but haven't until now... How well does the hook tool work ? It would seem that it would do a nice job of shearing inside a vessel. But I've wondered why that don't seem to be in the mainstream.

[Reed Gray]

John, by O1, do you mean drill rod? If so, the A2 is a harder material, and that is what is used on the tool rests.

As for tools and cost, I buy according to which tool will give me the best bang for the buck/best value/which one will make the most money for me...

robo hippy

[robert baccus]

I think we need to remember that the words hardened and tempering are not nouns but verbs. They represent many different types of technology and costs and are very complicated.

[Bill Boehme]

I've made hook tools using O-1 steel which is fairly easy to heat treat, but high speed steels, especially the powdered metal high speed steels have rather extreme heat treating requirements. For example, here is the process for Crucible CPM 10V on page 2.

[John K Jordan]

John, by O1, do you mean drill rod? If so, the A2 is a harder material, and that is what is used on the tool rests.

As for tools and cost, I buy according to which tool will give me the best bang for the buck/best value/which one will make the most money for me...

robo hippy

I've used A2 (and I think D2) drill rod but only had some already hardened.

I bought O1 steel because I found a good price on 1/8" thick flat stock and I understand it was relatively easy to machine and harden/temper. A2 is evidently harder but apparently there are tradoffs. Hock tools (I have some of their excellent knives) has this interesting article about the difference and why O1 might be better for sharp edges:

http://www.hocktools.com/tech-info/o1-vs-a2.html

For a long time I've been wanting to try making some scraping and cutting tools, including some knife blades - I think this winter I'll finally get some time! Working with tool steel from scratch is new to me so it may be an adventure. Fortunately I don't plan on making money from this; that might make it feel too much like work.

BTW, I've finally decided on a couple of things to make with a piece of that Mountain Mahogany, simple but useful - I post photos when done. That wood is special so I didn't want to be too hasty!

JKJ

[John K Jordan]

I think we need to remember that the words hardened and tempering are not nouns but verbs. They represent many different types of technology and costs and are very complicated.

Even the language is complicated. I believe hardened is actually an adjective but harden is a verb. It's all so confusing to me. Coincidentally I was thinking just yesterday about the seemingly increasing trend of "verbifcation" (verbing) of words in the English language. So I googled it.

JKJ

[Eugene Dixon]

JKJ. Channeling my metallurgy classes from 40 years ago, every steel (#) has a unique recipe. If you know the steel #, you know the chemistry. If you know the steel #/chemistry and can find the phase diagram for that mix of steel. With the phase diagram you have the beginnings of developing/tuning a heat treat and anneal process. With some trial and error (a.k.a., time and $$), you could be successful with the process.

I haven't looked at a phase diagram in 35 years, however.

Just my opinion.

[John K Jordan]

JKJ. Channeling my metallurgy classes from 40 years ago, every steel (#) has a unique recipe. If you know the steel #, you know the chemistry. If you know the steel #/chemistry and can find the phase diagram for that mix of steel. With the phase diagram you have the beginnings of developing/tuning a heat treat and anneal process. With some trial and error (a.k.a., time and $$), you could be successful with the process.

I haven't looked at a phase diagram in 35 years, however.

Just my opinion.

I finally hunted through the metals/machining shelf in my shop library and found Tubal Cain's book "Hardening, Tempering and Heat Treatment (Workshop Practice)" that I had forgotten about. I need a librarian.

https://www.amazon.com/Hardening-Tem.../dp/0852428375

I haven't read through it yet but fortunately Tubal Cain has a tendency to be more on the practical/how-to side than theoretical/technical side. I knew I bought that for a good reason nearly four years ago!

JKJ

[John Keeton]

Coincidentally I was thinking just yesterday about the seemingly increasing trend of "verbifcation" (verbing) of words in the English language. So I googled it.

JKJ

Just so you know someone “got” the pun!😉

[Larry Frank]

A phase diagram is not very useful for heat treating. The continuous cooling diagrams are useful showing what rate of cooling and temperatures are needed to achieve different microstructure and hardness.

One thing that happens is that as the price of alloy elements change, mfg may change the steels slightly that they use. They can still get very similar properties but at lower cost.